Ft. Lauderdale, Fla. — Episode 19 in the Great Republican Debate-a-thon may be most remembered for its spirited discussion of moon colonies. But it was Mitt Romney’s sharp performance that won the night in the last debate before Florida’s crucial primary next Tuesday.

Mr. Romney delivered his most confident answer to date on his wealth – that it is a source of pride, not a reason to apologize. He zinged his top rival for the Republican presidential nomination, Newt Gingrich, over an ad on immigration that he called “repulsive.” And he was ready with a comeback when Mr. Gingrich attacked him for having investments in Fannie Mae, Freddie Mac, and Goldman Sachs: Gingrich, he pointed out, has investments in mutual funds that invest in Fannie and Freddie.

Gingrich backed down. The audience, which in previous debates had energized the former House speaker, applauded most for Romney.

The debate in Jacksonville, Fla., capped the week with the highest stakes to date for Romney, the former governor of Massachusetts. He lost last Saturday’s primary to Gingrich by 12 percentage points, and needed a strong showing Thursday in a bid to retake momentum. The latest polls of Florida Republicans, taken after South Carolina and before the debate, show Romney may already be on his way: He has reversed his decline and is back on top.

Earlier this week, after facing intense pressure to release his tax returns, Romney finally obliged and put out two years’ worth. The confirmation that he had money invested abroad – including in a Swiss account – will certainly show up in President Obama’s arsenal against the wealthy former businessman, if Romney is the nominee. But on Thursday, Romney pivoted off Gingrich’s populism and found his voice on a matter that his supporters have been urging him to address in positive terms: his vast wealth.

“I'm proud of being successful; I'm proud of being in the free enterprise system that creates jobs for other people,” Romney said. “I'm not going to run from that.”

Romney also got an assist from debate moderator Wolf Blitzer of CNN. When Gingrich launched into his usual tactic of attacking a question, Mr. Blitzer didn’t back down, as CNN’s John King had a week ago during a debate in South Carolina.

Blitzer asked Gingrich if he was satisfied with Romney’s level of transparency over his tax returns. Gingrich called it “a nonsense question.”

“But Mr. Speaker, you made an issue of this this week when you said that he lives in a world of Swiss bank and Cayman Island bank accounts,” Blitzer said.

“If you make a serious accusation against Governor Romney like that, you need to explain that,” the moderator added, leaving Gingrich no choice but to reply. Romney thus had his opening: “I think it’s important,” he told Gingrich, “for people to make sure that we don’t castigate individuals who’ve been successful.”

Romney also channeled his inner Donald Trump when the discussion turned to the idea of building a moon colony, one of Gingrich’s pet proposals. The former speaker, in a bid for support from voters around Florida’s Kennedy Space Center, suggested that the government spur private-sector investment in space by offering prizes.

“I spent 25 years in business,” Romney said. “If I had a business executive come to me and say they wanted to spend a few hundred billion dollars to put a colony on the moon, I’d say, ‘You’re fired.’ ”

The immigration issue also loomed large in the debate, in a state with a fast-growing Latino population. The day before, Gingrich was scolded by the state’s most prominent Latino politician – Republican Sen. Marco Rubio – for running a radio ad that described Romney as the most “anti-immigrant” candidate. Gingrich took the ad down.

When Blitzer raised the issue, Romney called the idea that he’s the most anti-immigrant candidate “inexcusable,” noting that his father was born in Mexico (albeit to American parents, which he didn’t point out). “The idea that I’m anti-immigrant is repulsive,” he said.

Gingrich may still win points among Florida’s Latino Republicans for advocating leniency with older illegal immigrants who have been in the country a long time. But Romney had a retort: “Our problem is not 11 million grandmothers.”

Romney’s performance was not without mistakes. When asked about a radio ad by his campaign that said Gingrich had called Spanish “the language of the ghetto,” Romney said he didn’t think that ad came from his campaign. After a few moments, Blitzer indicated that CNN had checked, and that it was indeed a Romney ad. Gingrich asserted that the statement had been taken out of context.

The other two candidates on stage, Rick Santorum and Ron Paul, had their moments. Mr. Santorum, a former senator from Pennsylvania, skewered Romney over his reform of the Massachusetts health-care system, which is the model for Obama’s reform. And he delivered emotional responses to questions about how his religious beliefs would affect his presidency and why his wife would make a good first lady.

“She’s my hero,” Santorum said.

Congressman Paul of Texas, who is not competing in the Florida primary, got a laugh over a question about his health.

“I'm willing to challenge any of these gentlemen up here to a 25-mile bike ride any time of the day – in the heat of Texas,” Paul said to cheers.